This invention concerns air bag safety, systems and more particularly arrangements for providing air bag deployment openings in an interior trim structure, i.e., instrument panels, in which the outer surface does not give any visible indication of an air bag deployment door or opening.
Air bag systems have now come into common use for automotive vehicles, in which one or more air bags are stowed in respective storage spaces located within the passenger compartment. Typically, a driver's side air bag is stored in a receptacle in the center of the steering wheel and a passenger's side air bag is stored in a receptacle mounted behind the instrument panel. Upon detection of a relatively severe collision, the air bag or bags are very rapidly inflated and enter the passenger compartment to be deployed in positions within the passenger compartment so as to cushion the driver and/or passengers from injury which otherwise would be caused by impacting the interior structure of the auto.
The air bags must be neatly stowed out of sight and so as to be resistant to tampering, yet able to deploy into the passenger compartment in an instant . These requirements necessitate a sturdy closure panel for the deployment opening, preferably installed so as to minimize so as to any visual indication of the presence of the closure, and yet to reliably open under the wide range of ambient temperature conditions for which the auto is designed for use, over the entire useful life of the car (or truck).
Such closures are usually opened by a force exerted by the inflating air bag, and the deployment of the air bag must not be appreciably slowed by resistance developed in opening the closure. The considerable force applied by the inflating air bag must not result in fragmentation or separation of the closure, lest debris be projected towards persons in the passenger compartment.
The closure is of necessity exposed within the auto interior, and thus must be aesthetically compatible with the auto interior trim.
A vinyl skin covering layer is commonly applied to the instrument panel and other trim panel surfaces. Plastics such as vinyl, while durable, are relatively tough and resistant to tearing.
There has heretofore been proposed such closures in which doors are formed by a substrate panel overlain by a vinyl or covering layer skin, with the vinyl severed by the deploying air bag forcing the substrate panels against the inside of the covering layer. While preweakening of the covering layer has been utilized to facilitate severing, it is difficult to achieve reliable severing of this material at the appropriate force level.
U.S. Pat. No. 3,640,546 discloses a closure in which a pair of doors are covered by a covering skin, preweakened along a line of separation; which is ruptured when the doors are forced opened by the deploying air bag. The line of weakening is described as being accomplished by a reduction in thickness, perforating, or of heating. Such a joint is not sufficiently sturdy to resist inward pressure applied by an occupant and also results in a visible seam.
Various approaches have heretofore been devised to provide reliable severing of a vinyl covering layer for this purpose. See U.S. Pat. Nos. 4,991,870; 5,080,393; and 5,217,244, in which energy generating means are employed to degrade the vinyl skin over an air bag deployment opening.
Movable piercing cutters have also been proposed, see for example U.S. Pat. No. 4,989,896 which describes a piecing cutter positioned to be forced out by the air bag during deployment to penetrate the vinyl skin.
However, the remaining skin sections are severed by the pressure operated by the door being pushed open.
Another design challenge associated with piercing type cutters is to effectively transfer the energy of the inflating air bag to the cutters without disturbing the proper deployment of the air bag. Small area piercing point actuation cannot quickly and effectively absorb the pressure exerted by the air bag, since the area of the air bag is so much greater.
Also heretofore proposed is a "cookie cutter" type cf device, as described in U.S. Pat. No. 5,035,444, in which a large area pivoted cutter is swung out by contact with the inflating air bag. The cutter has a series of edges which are arranged in the shape of the deployment door free sides.
The vinyl covering layer is particularly difficult to cut when ambient conditions have heated it to an elevated temperature as the material tends to stretch considerably. Substantial loading is required to cut with the cutter shown in U.S. Pat. No. 5,035,444 when stretching occurs, and delayed completion of the cutting will retard air bag deployment and thus degrade or defeat the performance of the air bag system.
Further, the use of an extensive length of sharp cutting edge, directed outwardly, creates a possible danger to an occupant sought to be protected by the air bag.
Accordingly, the object of the present invention is to provide a mechanical arrangement for reliably cutting a vinyl covering layer to form an air bag deployment opening which arrangement completely and quickly cuts the covering layer in a pattern matching the deployment door sides, while minimizing the loading required to complete the severing of the covering layer. The object also is to minimize the hazards to the occupants by operation of the cutter.